A keyboard device is one of the widely-used computer peripheral devices. Via the keyboard device, the user may input characters or commands into a computer. With increasing development of science and technology, the keyboard device manufacturers make efforts in designing novel keyboard devices with diversified functions in order to meet the requirements of different users. Recently, an illuminated keyboard device with an illuminating function has been introduced into the market. Consequently, in case that the illuminated keyboard device is used in the dim environment with insufficient luminance, the characters marked on the keys of the illuminated keyboard device are still clearly visible to the user.
Hereinafter, the structure of a conventional illuminated keyboard device will be illustrated with reference to FIG. 1. FIG. 1 is a schematic cross-sectional view illustrating a conventional illuminated keyboard device.
Firstly, the components of the conventional illuminated keyboard device will be described. As shown in FIG. 1, the conventional illuminated keyboard device 1 comprises at least one key 11, a membrane switch circuit module 12, a supporting plate 13 and a backlight module 14.
The key 11 comprises a keycap 111, a scissors-type connecting element 112 and an elastic element 113. Moreover, the membrane switch circuit module 12 comprises an upper wiring plate 121 and a lower wiring plate 122. An upper contact 121a is formed on the upper wiring plate 121. Corresponding to the upper contact 121a, a lower contact 122a is formed on the lower wiring plate 122. Moreover, the backlight module 14 comprises a light guide plate 141, a reflective plate 142 and a light-emitting element 143.
The operating principle of the key 11 of the conventional illuminated keyboard device 1 will be illustrated in more details as follows. Firstly, the scissors-type connecting element 112 of the key 11 is connected with the keycap 111 and the supporting plate 13. The elastic element 113 is arranged between the keycap 111 and the supporting plate 13, and disposed within an accommodation space of the scissors-type connecting element 112. The membrane switch circuit module 12 is arranged between the elastic element 113 and the supporting plate 13.
As the key 11 is depressed, the keycap 111 is correspondingly moved with the scissors-type connecting element 112 in a vertical direction toward the supporting plate 13, and the membrane switch circuit module 12 is pushed by a protrusion part 113a within the elastic element 113. Under this circumstance, the upper contact 121a and the lower contact 122a of the membrane switch circuit module 12 are contacted with each other to be electrically conducted. Consequently, a corresponding input function is executed.
The illuminating principles of the conventional illuminated keyboard device 1 will be illustrated as follows. Firstly, the light guide plate 141 is located under the supporting plate 13, and the reflective plate 142 is located under the light guide plate 141. The light-emitting element 143 is located at a side of the light guide plate 141. The light-emitting element 143 may emit a light beam. The light beam is introduced into the light guide plate 141. Moreover, a portion of the light beam from the light-emitting element 143 is reflected by the reflective plate 142 so as to be projected upwardly toward the supporting plate 13 and transmitted through an opening 131 of the supporting plate 13. Moreover, the portion of the light beam is transmitted through a light-transmissible part of the keycap 111 so as to result in the illuminating efficacy.
However, the conventional illuminated keyboard device 1 still has the following drawbacks. Firstly, although the reflective plate 142 can facilitate the light beam to be reflected upwardly, a small portion of the light beam is transmitted through the reflective plate 142 because of the material of the reflective plate 142 of the conventional illuminated keyboard device 1. Since a portion of the light beam that is scattered downwardly is transmitted through the reflective plate 142, a portion of the light amount is lost. Secondly, although the light beam can be diffused into the whole light guide plate 141 after the light beam is introduced into the light guide plate 141, the light amount of the region farther from the light-emitting element 143 is less than the light amount of the region closer to the light-emitting element 143 because a portion of the light beam has been reflected out of the light guide plate 141 by the closer light-emitting element 143.
As mentioned above, the light utilization efficiency and the luminance uniformity of the conventional illuminated keyboard device 1 are not satisfied.
Therefore, there is a need of providing an improved illuminated keyboard device in order to overcome the above drawbacks.